Ballistic Fabric

ABSTRACT

Briefly the invention relates to a flexible fabric for use as for example in a roll-up shutter with improved ballistic properties. More specifically, the present invention is directed to a ballistic fabric that is formed from a unique cabled yarn and allows less deformation on impact. The unique cabled yarn may be a metal reinforced aramid yarn for giving the fabric additional strength.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority benefits of U.S. Provisional PatentApplication Ser. No. 60/874,108 filed Dec. 11, 2006 entitled “BallisticFabric”, the disclosure of which is incorporated herein by reference.

BACKGROUND

1. Field of the Invention

This invention relates generally to flexible fabrics with improvedballistic properties. More specifically, the present invention isdirected to a ballistic fabric that is formed from a unique cabled yarnand allows less deformation on impact.

2. Background Discussion

In south-east states like Florida and Louisiana, there is a need forprotecting the openings of buildings such as windows and doors and othermeans of access, especially after looking at the aftermath of HurricanesCharlie and Katrina. Often times such openings are covered withbreakable glass, and during a storm when a loose object, such as a treelimb or the like, is blown into the glass covering the opening, there isa danger that people within the building will be injured or killed bythe flying glass. For example, the states along the Gulf of Mexico,during certain times of the year, are prone to enormous and deadlystorms known as hurricanes. Hurricanes often have winds which blow above75 mph and between an average of 100 to 125 miles per hour, and in doingso, are able to blow foreign objects such as street signs, tree limbsand other types of debris into the windows of buildings, moreparticularly to individual homes within cities and towns affected by thestorm.

Shutters are mainly used to prevent flying debris from breaking theglass of the windows and letting the airflow into manufacturing plantsor residential houses. Most of the damage in hurricanes is caused by theair blowing into the premises through the broken windows and shutters,which then lifts off the roof and can cause the plant or house tocollapse. Preventing them from breaking prevents the majority of thedamage.

Rolling doors whose hanging portions are composed of individuallamella-type sections of metal or plastics material which are connectedto each other by means of hinges transversely of the rolling directionhave been known for decades. Rolling doors of this type can be movedonly slowly because they have mechanical hinges and produce unwanted,sometimes shrieking noises when they are moved. These rolling doors aresusceptible to damage during everyday operation, particularly due toimpacts from vehicles, such as, stacker trucks. The repair of the damageis complicated because deformed pans, such as, steel lamellas, aredifficult to replace.

Also known in the art are so-called high-speed doors which are composedof a relatively thin flexible hanging material made from webs of textileor plastics material. These doors can be moved several times faster. Inaddition, they can be made air-tight against wind. However, the majordisadvantage of these high-speed doors is the necessary complicatedmechanism because the highly flexible materials used in the doors arenot capable of transmitting thrust or pushing forces.

U.S. Pat. No. 6,286,579 discloses a retractable storm/hurricane shadesystem mountable on an exterior wall above a window, which containsvertical pockets into which PVC rods arc inserted. The rods are of alength such that when they are engaged with upper and lower ends of thewindow frame, they are slightly bowed out and provide additionalprotection against the impact of wind and flying objects. This set up,however, is not mechanically stable to withstand the damage caused dueto the impact of a hurricane storm.

U.S. Pat. No. 6,296,039 discloses an apparatus for wind-locking acurtain over an opening in a building. It is mounted on an exterior wallabove the window opening. A flexible corrugated curtain containshorizontal tension rods running in tracks on each side of the opening.The deployed curtain, similar to the previous one, is secured at thetop, bottom, and sides of the window. The curtain in this case also doesnot have sufficient impact resistance to withstand the colossal impactdue to a storm.

U.S. Pat. No. 5,353,858 discloses a reinforced closing element for anindustrial two-dimensional wall opening. The closing element is of aflexible material which can be rolled up and is reinforced transverselyof its rolling direction by bending-resistant reinforcement layers whichincrease the transverse stiffness and which are embedded on both sidesof a core zone within the closing element. This patent discloses thatthe elements can be formed of either textile or metal fibers, in whichcase, the closing element is either too flimsy or too stiff and does notprovide the essential ballistic properties required in a door closing.

U.S. Pat. No. 6,374,551 discloses a moveable structural reinforcementsystem with a moveable panel adapted to substantially close a buildingopening. The panel has shear load resistance means for regulating theshear stiffness of the building when the panel is in the closed positionto assist in resisting earthquake forces. This property, however, is notuseful in instances where the debris impacts the building surface athigh speeds.

U.S. Pat. No. 6,715,529 is a rolling shutter assembly including aplurality of interconnected metal slats. The slats travel in paralleltracks mounted on each side of the covered opening. The shutter willwithstand high wind velocities and forced entries without disengagementof the slats from the track.

Although there are many references directed to protective coverage foropenings, no patents disclose or teach a roll-up shutter that is bothflexible and strong and allows entry of light, making it ideal forexample a hurricane shutter system. Therefore, there was an immediateneed for a shutter that is flexible and strong, ideal for a hurricaneshutter system, something that incorporates reinforcing yarns andsomething that could be both flexible and ballistic at the same time.

As an existent solution to this problem, aramid based ballisticcloth/fabric have a well established application as a protective barrier(bullet proof vests, military vehicle body armor, aircraft enginecontainment, etc.) and therefore may be used. Most of these materialsare woven to less than 1 m widths in very dense, multiply structureswith no open area. However, as a result of the stranded nature of aramidmaterials, producing wide width (1-12 m) panels of open mesh designs forprotection of large objects like windows for housing, office, orbusiness store fronts is often not feasible. Yarns produced of aramidstrands tend to dimensionally flatten during weaving producing a fabricwith little open area/porosity and poor dimensional stability as aresult of the lack of crimp in the aramid yarns. Additionally, aramidyarns are difficult to weave as the individual strands that make up anaramid yarn, while having good tensile strength tend to abrade resultingin continuous breaks across the width during weaving. The wider theweaving width, the larger the variation in tension and degree ofbreakage across the face of the fabric produced.

Therefore, there is a void space in this area and the present inventionprovides for filling this void space with a ballistic hurricane shutterthat overcomes the drawbacks of the prior art discussed above andtherefore would be an advancement in the state of the art.

SUMMARY OF THE INVENTION

Briefly the invention relates to a flexible fabric, for example aroll-up shutter with improved ballistic properties. More specifically,the present invention is directed to a ballistic fabric that is formedcontaining unique cabled yarns. The unique cabled yarn may be a metalreinforced aramid yarn giving the fabric additional strength, andallowing less impact deformation.

Accordingly, one embodiment of the present invention is directed to acabled metal reinforced aramid yarn for use in high-strength,high-modulus applications such as industrial, commercial or consumershutters.

Another embodiment is directed to a ballistic fabric made from cabledmetal reinforced aramid yarns that have enhanced ballistic propertiesand may be used in industrial applications such as industrial plantdoors, shutters or coverings.

Yet another embodiment of the present invention is directed to ahurricane shutter made from cabled metal reinforced aramid yarns and hasimproved flexibility as well as enhanced ballistic properties.

Yet another embodiment of the present invention provides for the shutterhaving a variety of weave patterns based on the required characteristicsof the fabric.

Yet another embodiment of the present invention provides for the shutterwhose yarns are UV coated for outdoor exposure of such a fabric.

Yet another embodiment of the present invention is directed to aballistic fabric made from yarns with aramid strands that are used as acore material within a thermoplastic sheath. As with the use of thecabled steel, the thermoplastic sheath allows for the maximum strengthof the aramid core to be realized, protects the aramid fromabrasion/cutting, maintains diameter uniformity, and allows for crimpgeneration via plastic deformation of the sheath.

Yet another embodiment of the present invention is directed to ahurricane shutter made from yarns comprising aramid strands that areused as a core material within a thermoplastic sheath, which shutter hasimproved flexibility as well as enhanced ballistic properties.

Other embodiments of the present invention include fabrics describedabove but implemented using different weave patterns and yarncombinations with one or more layers in conjunction with one or morecoatings to the cabled yarn.

BRIEF DESCRIPTION OF THE DRAWINGS

To the accomplishment of the foregoing and related ends, certainillustrative aspects of the invention are described herein in connectionwith the following description and the annexed drawings. These aspectsare indicative, however, of but a few of the various ways in which theprinciples of the invention may be employed and the present invention isintended to include all such aspects and their equivalents. Otheradvantages and novel features of the invention may become apparent fromthe following description of the invention when considered inconjunction with the drawings. The following description, given by wayof example, but not intended to limit the invention solely to thespecific embodiments described, may best be understood in conjunctionwith the accompanying drawings, in which:

FIGS. 1-3 illustrate the problems associated with weaving an aramidbased ballistic fabric;

FIG. 4( a) illustrates the cabled metal reinforced aramid yarn accordingto one embodiment of the present invention;

FIG. 4( b) illustrates the breaking of a cabled metal reinforced aramidyarn at the aramid's maximum tensile strength;

FIG. 5 illustrates the ballistic fabric according to one embodiment ofthe present invention; and

FIG. 6 shows a cross-section of the yarn according to one embodiment ofthe present invention.

DETAILED DESCRIPTION

It is noted that in this disclosure and particularly in the claimsand/or paragraphs, terms such as “comprises,” “comprised,” “comprising,”and the like can have the meaning attributed to it in U.S. patent law;that is, they can mean “includes,” “included,” “including,” “including,but not limited to” and the like, and allow for elements not explicitlyrecited. Terms such as “consisting essentially of” and “consistsessentially of” have the meaning ascribed to them in U.S. patent law;that is, they allow for elements not explicitly recited, but excludeelements that are found in the prior art or that affect a basic or novelcharacteristic of the invention. These and other embodiments aredisclosed or are apparent from and encompassed by, the followingdescription.

Aramid based ballistic cloth/fabric have a well established applicationas a protective barrier (bullet proof vests, military vehicle bodyarmor, aircraft engine containment, etc.) and therefore may be used inthis area. Most of these materials are woven to less than 1 m widths invery dense, multiply structures with no open area. However, as a resultof the yarns comprising strands of aramid materials, producing widewidth (1-12 m) panels of open mesh designs for protection of largeobjects like windows for housing, office, or business store fronts isoften not feasible. Yarns of aramid strands or filaments tend todimensionally flatten during weaving producing a fabric with little openarea/porosity and poor dimensional stability as a result of the lack ofcrimp in the aramid yarns. Additionally, aramid yarns are difficult toweave as the individual strands that make up an aramid yarn, whilehaving high tenacity tend to have continuous breaks 10 across the widthduring weaving, as shown in FIGS. 1 and 2. The wider the weaving width,the larger the variation in tension and degree of breakage across theface of the fabric produced. As an example, the fabric showed in FIG. 3,formed from aramid yarns in the machine direction (“MD”) and metal orstainless steel yarns in the cross-machine direction (“CD”), has fuzzyyarns 20 all over the surface of the fabric due to frequent yarn breaksduring weaving. This creates undesired effects in the fabric and couldalso cause the fabric to fail on impact. Therefore, the presentinvention is directed to producing a fabric that is ballisticallyfunctional while retaining the aesthetics, open area and porosity of anopen fabric.

The invention according to one embodiment of the invention is aballistic fabric 100 made from cabled metal reinforced aramid yarns 80that has enhanced ballistic properties and this fabric may be used inindustrial applications such as industrial plant doors, or windowshutters or coverings. In the cabled yarn 80, the metal part or strand60 imparts additional strength and yarn “crimping” to stabilize theweave, while the aramid part 50 of the yarn imparts flexibility as wellas impact resistance to the fabric. In any ballistic fabric, twofeatures are most important in reducing the fabric's deformation:reinforcement beams and the mass of the fabric. The cabling of metalstrands 60 with aramid strands 50 produce yarns which satisfy both theseconditions in the present invention.

The invention according to another embodiment of the invention is aroll-up shutter fitted to cover the outside of residential windows toprotect the window glass from breakage by tropical storm-type winds. Theshutter can be made from cabled metal reinforced aramid yarns 80 of thepresent invention, which shutter has enhanced ballistic properties.

Specifically, the invention involves the use of modified aramid yarns toaddress the shortcomings of the straight aramid yarns outlined above.According to one embodiment, this invention uses yarn 50 that usesaramid as a core material in a cabled stainless steel structure 80. Asshown in FIG. 4( a), steel strand 60 is wrapped, twisted or cabledaround an aramid core 50 so as to obtain the benefits such as: (a)maintaining the strength of the aramid material 50 by allowing for moreelongation of the steel strands 60 under tensile stress, which allowsfor the steel 60 to break at the aramid 50 break elongation (shown inFIG. 4( b)); (b) protecting the aramid strands 50 from abrasion/cuttingduring weaving; (c) maintaining diameter uniformity of the strandsduring weaving to maintain mesh/count, open area, and air permeability;(d) developing crimp in the final woven fabric via deformation of thecabled steel; and (e) allowing for production of uniform fabric in anywidth, especially widths wider than 1 m.

In a preferred embodiment of the present invention, the ballistic fabric100 is produced using for example a 0.76 mm yarn, which is produced bycabling for example a 1420 denier Kevlar® 49 yarn 50 with for example a6×0.20 mm 316L stainless steel wire 60 with for example 5 twists/cm, asshown in FIG. 4( a). The mesh count for a fabric thus produced may befor example 5×4 strands per cm.

Aramids used can be made of various grades/manufacturers such as Nomex®although the Kevlar® 49 type is preferred for maximum ballisticstrength. Other materials for yarns such as certain polyethylenes likeDyneema® and Spectra® may also be used for this purpose. Steel type isnot critical although stainless is preferred. A UV coating may beapplied to the fabric or the component yarns individually for outdoorexposure of such a fabric.

According to another embodiment, the invention uses yarns comprisingaramid strands that are used as a core material 30 within athermoplastic sheath 40 as shown in FIG. 6. As with the use of thecabled steel, the thermoplastic sheath 40 allows for maximum strength ofthe aramid core 30 to be realized (via elongation of the sheath, whichis greater than the aramid), protects the aramid 30 fromabrasion/cutting, maintains diameter uniformity, and allows for crimpgeneration via plastic deformation of the sheath 40.

In a preferred embodiment of the invention, the ballistic fabric 100 isproduced as using for example a 0.76 mm strand 70 produced using forexample a 1420 denier Kevlar® 49 yarn 30 of 0.33 mm diameter and forexample a black UV stabilized polyethylene terepthalate sheath 40applied over the core Kevlar® strands 30. This yarn may be produced byfor example a cross head extrusion method or a coating process. The meshcount for a fabric thus produced may be for example 5×4 strands per cm.

Aramids can be used of various grades/manufacturers such as Nomex®although the Kevlar® 49 type is preferred for maximum ballisticstrength. Other materials for yarns such as certain polyethylenes likeDyneema® and Spectra® may also be used for this purpose. The UV coatingmay be applied to the fabric or the component yarns individually foroutdoor exposure of such a fabric.

The fabric described in different embodiments of the invention can beconstructed with various weave patterns known in the art including lenoweaves. Combination of materials listed in different embodiments, forexample cabled aramid-steel yarns and sheath core yarns, can also beemployed to meet the desired ballistic properties of the fabricstructure. The fabric may also be formed by combining cabledaramid-steel yarns 80 and sheath-core yarns 70 in either CD or MDdirections, as shown in FIG. 5 and yarns in either direction may not belimited to the same type and may comprise a combination of yarn types.

The fabric can also be made via techniques such as knitting or braidinginstead of weaving. Depending upon the width or length of the shutterrequired techniques to form the braided or knitted sections together maybe employed.

Although illustrative embodiments of the invention have been describedin detail herein with reference to the accompanying drawings, it is tobe understood that the invention is not limited to those preciseembodiments, and that various changes and modifications can be effectedtherein by one skilled in the art without departing from the scope andspirit of the invention as defined by the appended claims.

1. A ballistic fabric for use in a roll-up shutter or the like, thefabric comprising: a plurality of cabled yarns in MD and CD directions;wherein said cabled yarns are formed by cabling high tenacity aramidyarns with metal.
 2. A method for producing a ballistic fabric, themethod comprising the steps of: cabling high tenacity aramid yarns withmetal; and weaving said cabled yarns in a preferred pattern to apredetermined width.
 3. A ballistic fabric for use in a roll-up shutteror the like, the fabric comprising: a plurality of composite yarns in MDand CD directions; wherein said composite yarns are formed from aramidstrands used as a core material within a thermoplastic sheath.
 4. Amethod for producing a ballistic fabric, the method comprising the stepsof: producing composite yarns with aramid strands used as a corematerial within a thermoplastic sheath; and weaving said composite yarnsin a preferred pattern to a predetermined width.
 5. The fabric accordingto claim 1, wherein said yarns are UV coated for outdoor exposure ofsaid fabric.
 6. The fabric according to claim 1, wherein the metal isstainless steel.